had beenThird conditional: "If adequate precautions _____ taken, the disaster could have been prevented."If adequate precautions had been taken, the disaster could have been prevented.NoteIf adequate precautions had been taken, the disaster could have been prevented.Elon.io is an online learning platformWe have an entire course teaching IELTS Vocabulary — Band 7+ grammar and vocabulary.Start learning IELTS Vocabulary — Band 7+ now